Fluid Displacement Research Articles

Pore-scale investigation of immiscible fluid displacement process in randomly distributed bead-based porous micromodels using Micro-PIV

This study reports pore-scale immiscible displacement processes in a bead-based porous micromodel using fluorescence microscopy and micro-particle image velocimetry (μ-PIV) technique. The porous micromodels with heterogeneous and homogeneous geometry are fabricated to investigate the effect of displacing phase viscosity and flow rate on the pore-scale displacement mechanism. The phenomena of shear-induced circulations and viscous instability are observed during the displacement of the trapped non-wetting phase through the porous domain. Breakage and coalescence of the droplets of the non-wetting phase were also observed during the displacement process. The velocity vector maps show that there is frequent flow reversal of ganglia, leading to an unsteady flow behaviour during the displacement process. The effect of flow rate and viscosity on the trapped non-wetting phase is investigated, and the results obtained indicate that an increase in the flow rate reduces the trapped non-wetting fluid saturation in the porous medium by disintegrating large ganglia into small droplets. Increasing either the flow rate or viscosity increases the shear stress at the interface of the trapped ganglion and displacing phase, leading to shear-induced circulations, and the strength of the vortex is found to increase. These circulations inhibit further displacement of the trapped fluids. At higher flow rate with more viscous displacing phase, the trapped non-wetting phase ganglion disintegrate into smaller droplets. It is observed that a heterogeneous micromodel causes significant trapping and lesser mobilization of the non-wetting phase compared to a homogeneous system. The porous medium with low porosity and a higher degree of heterogeneity results in more trapping and less recovery of the non-wetting phase.

An insight into core flooding experiment via NMR imaging and numerical simulation

Traditional core flooding experiments can only be used post breakthrough while what happens in the core prior to this time is vital to understand multiphase flow phenomenon for more successful EOR operations. We can overcome this obstacle through a visualized fluid displacement scheme. This can ultimately provide us with a reliable relative permeability curve that can lead to a more accurate reservoir simulation outcome in the field scale. In this study, NMR imaging is employed in a water flood experiment in conjunction with two separate numerical two-phase flow simulation methods (FDM and FEM), to reproduce experimental data. Using the Brooks-Corey equation, random pore size distribution indices (λ) are selected to generate relative permeability curves. Moreover, simulations are performed with FDM, and oil displacement efficiency, saturation maps, and saturation profiles are generated and compared to the experimental results. Next, FEM was employed in COMSOL for further validation and FDM results were found in agreement with the experiments. This way, an appropriate relative permeability curve was generated and assigned to the sample. Results suggest that λ of 0.2 generated the best numerical results with an MSE value of 0.009 in oil displacement efficiency curves, comparable to the experiments. Collectively, integration of imaging techniques with routine experimental fluid displacement procedures presented a detailed insight into complicated nature of multiphase flow phenomena in geomaterials.

Spaceflight-associated neuro-ocular syndrome: a review of potential pathogenesis and intervention.

With the continuing progress in space exploration, a new and perplexing condition related to spaceflight ocular syndrome has emerged in the past four decades. National Aeronautics and Space Administration (NASA) has named this condition "spaceflight-associated neuro-ocular syndrome" (SANS). This article gives an overview of the current research about SANS and traditional Chinese medicine (TCM) by analyzing the existing publications on PubMed and CNKI and reports from NASA about SANS, summarizing the potential pathogenesis of SANS and physical interventions for treating SANS, and discussing the feasibility of treating SANS with TCM. Due to the unique characteristics of the space environment, it is infeasible to conduct large-scale human studies of SANS. SANS may be the result of the interaction of multiple factors, including inflammation and fluid displacement in the optic nerve sheath and cerebrospinal fluid. We should pay attention to SANS. Visual function is not only related to the health of astronauts but also closely related to space operations. TCM has antioxidative stress and antiapoptotic effects and is widely used for optic nerve diseases. TCM has great potential to prevent SANS.

Surface Charge Affecting Fluid–Fluid Displacement at Pore Scale

AbstractEfficiency in fluid–fluid displacement is drastically reduced by viscous fingering, limiting the overall effectiveness in enhanced oil recovery, membrane science, and lateral flow devices used in biomedical applications. Local instabilities at the fluid–fluid interface lead to finger‐like patterns when a less viscous fluid displaces an immiscible fluid of higher viscosity. This widely observed phenomenon in multiphase flow inside porous media is infamously intricate to control, especially for given geometry and viscosity ratio. The presented study uses a highly controlled microfluidic porous network structure with tailored ionic surface strength. The direct correlation of viscous fingering evolution on the porous structure's zeta potential at a pore‐scale level is demonstrated via polyelectrolyte coatings using a layer‐by‐layer technique. Displacement patterns are tuned from vigorous viscous fingering over stable displacement to corner flow events across a broad range of capillary numbers depending on the applied coatings. The experimental data show an increasing trend of oil recovery with increasing surface wettability, consistent with several previous findings. Furthermore, the results reveal that surface zeta potential correlates positively with recovery rate but negatively with the displacement stability quantified by the fractal dimension. These insights enable a more targeted porous media design to obtain optimal multiphase flow control.

Insights on electromagnetic scattering by steel casings in surface-to-borehole and borehole-to-surface methods

The development of surface-hole electromagnetic technologies has gained renewed interest in recent years. This is motivated by the method's capability to provide the sensitivity of the resistivity distribution in a hydrocarbon reservoir and its variation over time associated with fluid displacement. However, it has been long recognized that data acquired in a realistic experimental setting will carry a distorting component to the measured fields, superimposed to those expected in an idealized open-hole setup. Investigating the processes driving the casing effect can lead to properly identifying distortions of the measurements and ultimately defining adequate strategies to deal with the inversion of casing-contaminated data sets. In this paper, I discuss the main aspects of the electromagnetic physics behind the conceptual model and describe current channeling and radial flow arising when the formation is excited by sources embedded inside the pipe. I revisit these concepts to explain measurement distortion of receivers placed in the vicinity of the casing, describe measurement sensitivity of resistive targets in surveys deploying casing antennas, and review suitable strategies for the inversion of casing-distorted data. I also briefly outline active topics of research intended to provide further insight to better understand the casing effect.

An improved multicomponent pseudopotential lattice Boltzmann method for immiscible fluid displacement in porous media

Immiscible fluid displacement in porous media occurs in several natural and industrial processes. For example, during petroleum extraction from porous rock reservoirs, water is used to displace oil. In this paper, we investigate the primary drainage and imbibition in a heterogeneous porous medium using an improved numerical model based on the multicomponent pseudopotential lattice Boltzmann method. We apply recent developments from the literature and develop new pressure boundary conditions. We show that the proposed model is able to simulate realistic viscosity ratios, and it allows independent tuning of surface tension from viscosity. Moreover, the model suppresses a nonphysical behavior of previous schemes, in which trapped fluid volumes significantly change with time. Furthermore, we show that the developed model correctly captures the underlying physical phenomena of fluid displacements. We simulate oil–water flows and verify that the measured values of irreducible water and residual oil saturations are realistic. Finally, we vary the wetting conditions of the porous medium to represent different wettability states. For the different scenarios, we show that the simulations are in good agreement with the experimental results.

Oil secondary migration simulation in tight reservoir and fingering factors analysis

In the tight reservoirs, the oil accumulation is characterized by ambiguous trap boundaries, complicated oil distribution and nano-scale pore-throat interconnection system. As one of significant process for understanding the oil trap in the tight reservoir, oil migration from source rocks to reservoirs is the key concern by geoscientist. Investigating the immiscible two-phase fluids displacement in porous media, especially the fingering problem during the hydrocarbon migration, has always been a challenge scientific topic. This study establishes PNMs (Pore Network Model) with multiple viable parameters. A fluid migration numerical program is built for the flow study by modifying Poiseuille equation. Sensitive studies have been conducted by several dimensionless numbers to investigate the control factors of the flow behavior. Five factors are identified as the key factors on the migration mode: 1) Fluid viscosity ratio; 2) Interface tension force; 3) Fluid density; 4) Pore structure of sediments; 5) Capillary number. Oil migration behavior is affected by pressure domain, buoyancy, and resistance forces, such as capillary resistance and viscous forces. As the distribution fractal dimension increases with a given viscosity ratio, the width of the front edge of oil-water interface gradually expands. Oil saturation increases in parallel with a rising capillary number. During the simulation, Haines Jump phenomenon is observed. When the capillary number increases, oil migration gravitates towards piston-like displacement. As the oil-water viscosity ratio increases, the front width reaches its maximum at a particular point in time, and plateaus.

Study on temperature distribution prediction of horizontal wells during fracturing treatment

In recent years, fiber-optic distributed temperature sensors (DTS) have been widely used for the dynamic monitoring of horizontal well during fracturing treatments. It is proposed to address the frequent issues of unknown artificial fracture initiation location, unclear crack extension pattern, unknown fracturing fluid injection success, and difficult fracturing effect evaluation in the hydraulic fracturing of horizontal wells. The temperature prediction model is the basis for fracturing diagnosis based on DTS monitoring, however, the quantitative prediction of temperature distribution throughout the horizontal well fracturing process remains a challenge. In this paper, a set of temperature-distribution prediction model for multi-stage fracturing in horizontal wells is established, with various micro-heat effects taken into account, and the models are solved through coupling. The temperature distribution during multi-cluster fracturing, and the temperature distribution characteristics during staged fracturing of horizontal wells have been analyzed. Moreover, the influence of fracturing fluid displacement, formation filtration coefficient, fracture width, and height on temperature distribution has also been clarified. The findings of this study provide theoretical support for fracturing performance diagnosis, fracture initiation identification, and analysis of the whereabouts of fracturing fluids using DTS monitoring. It has a great significance on fracturing effect evaluation and fracturing design optimization for horizontal wells.

Horizontal miscible displacements through porous media: the interplay between viscous fingering and gravity segregation

We consider miscible displacements in two-dimensional homogeneous porous media where the displacing fluid is less viscous and has a different density than the displaced fluid. We find that the dynamics evolve through nine possible regimes depending on the viscosity ratio, strength of density variations and the strength of the background flow, as characterized by the Péclet number. At early times the interface is dominated by longitudinal diffusion before undergoing a transition to a slumping regime where vertical flow is important. At intermediate times, vertical flow and diffusion can be neglected and there are three different limiting solutions: a fingering limit; an injection-driven gravity-current limit; and a density-driven gravity-current limit. Finally at late times, transverse diffusion becomes important and there is a transition from an apparent shutdown regime to a viscously enhanced Taylor-slumping regime. In each of the regimes, the dominant scalings are identified and reduced-order models for the evolution of the concentration field are developed. Lastly, three case studies are considered to illustrate the dominant physical balances in the geophysically relevant setting of geological $\textrm {CO}_2$ storage.

Contact angle hysteresis: A new paradigm?

The wetting of a surface by a liquid is a crucial part of many natural and industrial processes. Despite numerous existing studies, some elements of wetting-drying such as contact angle variation during flow, are still poorly understood, yet it is a crucial piece of information needed for modeling fluid displacements in capillary-dominated flows. In the context of multi-phase flow in porous media, scarcity of direct contact angle measurements inside pores (in-situ) has added to the ambiguity. This work presents an unprecedented study of contact angle variations at different stages of flow, for a variety of fluid systems, using direct pore-scale measurements. Observations reveal that on average, contact angle patterns depend strongly on the type of nonwetting fluid: dodecane and decane, for instance, show large contact angle hysteresis between drainage (drying) and imbibition (wetting) cycles, while air or Soltrol® 220 oil exhibits little hysteresis. To further explore this behavior, we evaluate contact angle from the perspective of geometry, and show that the combined effects of fluid-fluid curvature and wetted-pore-radius variations can explain the observed trends. We hypothesize that, for certain nonwetting fluids, fluid-solid chemical interactions lead to pinning of fluid interfaces and the fairly enhanced hysteresis observed for some nonwetting fluids. Overall, this study suggests that contact angle is a result of the interplay between pore geometry and the forces deforming the fluid interface (including surface chemical interactions), and thus, - despite traditional practice -, contact angle alone is not always an accurate metric for wettability.

Divergence‐free finite elements for the numerical solution of a hydroelastic vibration problem

AbstractIn this paper, we analyze a divergence‐free finite element method to solve a fluid–structure interaction spectral problem in the three‐dimensional case. The unknowns of the resulting formulation are the fluid and solid displacements and the fluid pressure on the interface separating both media. The resulting mixed eigenvalue problem is approximated by using appropriate basis of the divergence‐free lowest order Raviart–Thomas elements for the fluid, piecewise linear elements for the solid and piecewise constant elements for the interface pressure. It is proved that eigenvalues and eigenfunctions are correctly approximated and some numerical results are reported in order to assess the performance of the method.

Effects of grain shape and packing pattern on spontaneous imbibition under different boundary conditions: Pore-scale simulation

Core-scale spontaneous imbibition experiments and numerical simulations have demonstrated that the macroscopic imbibition performance is significantly different under different boundary conditions. However, the detailed pore-scale flow mechanisms behind these phenomena and the influence of porous media's geometric features on the imbibition behavior under different boundaries have not been addressed in depth. In this work, an optimized color-gradient lattice Boltzmann model is applied to simulate spontaneous imbibition in granular media under four boundary conditions. The influence of grain shape and packing pattern on the two-phase interface evolution and the recovery factor during spontaneous imbibition is investigated while fixing different models' porosity, grain number, and size distribution. It is found that the grain shape has little influence on the drainage interface evolution at the initial stage but it has a more significant influence on the imbibition interface during counter-current spontaneous imbibition. The grain packing pattern influences the evolution of drainage and imbibition interfaces and the recovery factor. Spontaneous imbibition with different boundary conditions has different imbibition rates and ultimate recovery factors. The fastest imbibition rate and highest ultimate recovery are obtained under all faces open and two faces open (free) boundary conditions, respectively. This research provides pore-scale insights into the complex dynamic fluid displacement mechanism between the fracture and matrix of fractured oil and gas reservoirs.

Transition from viscous fingers to compact displacement during unstable drainage in porous media

The immiscible displacement of a viscous fluid by a less viscous one in a porous medium is known to be unstable and often results in dendritic fingering patterns, where the pressure gradient is screened internally and only advanced invading parts grow. We present experiments in porous media, systematically varying the imposed injection pressure ($P$) and viscosity ratio ($M$) of the invading to defending fluid. A crossover to more stable and compact invasion structures is found for higher $P$ and $M$. This compact invasion regime onset is observed even for $M<{10}^{\ensuremath{-}3}$. We show that the pressure gradient is not screened in this regime and invasion patterns exhibit rich internal flow dynamics.

The study of hydraulic fracture height growth in coal measure shale strata with complex geologic characteristics

The coal measure shale strata (CMSS) is rich in coalbed methane and shale gas. However, different thicknesses and high heterogeneity between the coal and shale typically result in difficultly predicting hydraulic fracture height growth. The feasibility of multi-gas production and the optimal layer for fracturing in CMSS requires a better understanding of fracture vertical propagation mechanism. In this paper, a three-dimensional model of a hydraulic fracture crossing CMSS layer was built according to geological characteristics, based on the rock seepage-stress-damaged coupled finite element method. The influence of geological factors and construction factors on the hydraulic fracture expansion was investigated. The results showed that (1) The physical property and geological conditions presented a huge difference between different lithological rock with various depth; (2) The increase of displacement and fracturing fluid viscosity, the inhibition effect on vertical fracture extension became weak. The augment of displacement was more helpful to the vertical propagation of fracture; (3) Under low permeability difference and small horizontal minimal principal stress difference, fracture length propagated enough distance and fracture height extension gap connected more the production layer. Therefore, the favorable conditions for forming balanced fracture geometry were as follows: permeability difference from 0–3 and stress difference from 1–2 MPa. (4) The 11th layer was chosen as the best fracturing layer in Shanxi Formation. The fracture height was about 26.13 m and the thickness of pay layers accounted for 42.32% of the height. The research results provide theoretical guidance for the optimal fracturing layer and fracturing construction parameters in CMSS.

Axisymmetric transient response of a cylindrical cavity in an unsaturated poroelastic medium

In this study, the transient response of an infinite unsaturated poroelastic medium with an infinitely long uniform cylindrical cavity subjected to axially symmetric transient radial tractions is investigated. Using the Laplace transform, analytical solutions are obtained for three different types of prescribed transient radial pressures (step, gradually applied step, and triangular pulse loads) acting on the surface of a permeable cavity and that of an impermeable cavity. The time histories of the radial displacement, stresses, pore pressure, and discharge are derived by inverting the Laplace domain solutions using a reliable numerical scheme. The solution can be simplified to one in which the infinite medium is assumed to be a saturated poroelastic medium. The validity of the solution was confirmed by comparison with COMSOL numerical solutions. A detailed parametric study is presented to illustrate the influence of the saturation of the unsaturated poroelastic medium on the response of the radial displacement, hoop stress, and pore fluid pressure at the cavity surface under different boundary conditions.

Mixed approximation of the axisymmetric acoustic eigenvalue problem

The aim of this paper is to study the numerical approximation of mixed formulations for the acoustic eigenvalue problem with axial symmetry. It is well known that, in the full three-dimensional problem, using Raviart–Thomas elements for the fluid displacements yields a discretization free of spurious eigenvalues. However, it has been recently shown that this is not the case in the axisymmetric pure displacement formulation. Two mixed formulations are introduced in order to avoid the spurious modes. A discretization based on Raviart–Thomas mixed method is proposed and analyzed. We provide a convergence result under rather general conditions, as well as absence of spurious modes. Moreover, we prove quasi-optimal order error estimates under additional regularity assumptions. Finally, we report numerical results which allow us to confirm the theoretical estimates.

Physiological Changes Associated with Space Missions: How Physical Exercise Helps

Physiological Changes Associated with Space Missions: How Physical Exercise Helps

Measuring Orthopedic Plate Strain to Track Bone Healing Using a Fluidic Sensor Read via Plain Radiography.

We describe a fluidic X-ray visualized strain indicator under applied load (X-VISUAL) to quantify orthopedic plate strain and inform rehabilitative care. The sensor comprises a polymeric device with a fluidic reservoir filled with a radio-dense fluid (cesium acetate) and an adjoining capillary wherein the liquid level is measured. A stainless-steel lever attaches to the plate and presses upon the acrylic bulb with a displacement proportional to plate bending strain. The sensor was attached to a plate in a Sawbones composite tibia mimic and a human cadaveric tibia. An osteotomy model (5 mm gap) was used to simulate an unstable fracture, and allograft repair to simulate a stiffer healed fracture. The cadaveric and Sawbones tibia were cyclically loaded five times (0-400 N) using a mechanical test stand, and fluid displacement was measured from plain radiographs. The sensor displayed reversible and repeatable behavior with a slope of 0.096 mm/kg and fluid level noise of 50-80 micrometer (equivalent to 5-10 N). The allograft-repaired composite fracture was 13 times stiffer than the unstable fracture. An analysis of prior external fracture fixation studies and fatigue curves for internal plates indicates that the threshold for safe weight bearing should be 1/5th-1/10th of the initial bending for an unstable fracture. The precision of our device (<2% body weight) should thus be sufficient to track fracture healing from unstable through safe weight bearing. The X-VISUAL fluidic sensor enables orthopedic plate strain quantification to monitor facture healing via X-ray imaging.

A lattice Boltzmann study of miscible displacement containing dissolution reaction in porous medium

The miscible displacement with fluid-solid dissolution reaction in a porous medium is a typical process in many industrial applications, such as underground-water pollution decontamination, and oil recovery or geological sequestration of carbon dioxide. It is a significant problem in engineering and physics applications. As is well known, the dissolution reaction can change the structure of the porous medium, which will have a great influence on the miscible displacement process. However, the relationship between the displacement process and the dissolution reaction in a porous medium has not been fully studied. In this study, the miscible displacement with dissolution in a porous medium is simulated by a lattice Boltzmann method (LBM). The study focuses on the influence of the internal structure change on the displacement process, and the further quantitative analyzing of the changes of the porosity and displacement efficiency by changing the Damkohler number (&lt;i&gt;Da&lt;/i&gt;) and the Pèlcet number (&lt;i&gt;Pe&lt;/i&gt;). The results show that when&lt;i&gt; Da&lt;/i&gt; is large enough, the dissolution reaction will generate a few wormholes in the porous medium, and the displacement fluid will leave the porous medium along the wormholes, resulting in the decrease of the displacement efficiency. As &lt;i&gt;Da&lt;/i&gt; increases, the reaction goes faster, the rate of change in porosity increases, and the wormholes become wider, thereby indeed yielding a larger displacement efficiency. With the increase of &lt;i&gt;Pe&lt;/i&gt;, the fingerings develop faster, the rate of change in porosity decreases, and the displacement efficiency decreases as well.

Numerical Investigation of Enhanced Oil Recovery from various Rocks by Nanosuspensions Flooding

This work is devoted to the systematic numerical simulation of oil displacement using nanosuspension with silicon oxide particles with concentration of up to 1 wt% and particle sizes of 5 nm. The influence of such factors as core wettability, concentration of nanoparticles, capillary number, and oil viscosity on the enhanced oil recovery by nanosuspension has been systematically investigated using the VOF method for 2D-dimensional micromodels. Various rocks were considered: dolomite, metabasalt and sandstone. It is shown that the oil recovery coefficient improves for all considered types of rock with increasing nanoparticle concentration. The most effective application of nanosuspension for enhanced oil recovery is observed at a low capillary number, corresponding to the capillary displacement mode. The addition of nanoparticles facilitates increasing oil recovery factor in a wide range of viscosity ratios between oil and displacement fluid.